Ozone, or O.sub.3, is an allotropic form of oxygen that exists as an unstable blue gas. Ozone readily is produced from air or other oxygen containing gas by passage of a high voltage electrical discharge through a stream of the oxygen-containing gas.
Ozone is an active oxidizing agent that destroys bacteria, viruses and other microorganisms on contact. Low levels of ozone are excellent for eliminating unpleasant odors in air, destroying pollen and dust particles, and even killing bacteria that may be floating in the air or on surfaces in contact with the air. Unlike many other disinfecting agents, ozone is used as it is generated, breaks down rapidly and does not leave chemical residues. Ozone reverts to oxygen with a half life that can be as much as several hours in the absence of oxidizable matter.
However, ozone can be toxic in sufficient concentrations over a sufficient period of time. Ozone at lower concentrations is considered substantially non-toxic but exposure to a sufficient amount over a prolonged period can produce adverse symptoms in humans and other mammals and can irritate the eyes, nasal passages, and throat. Exposure to ozone for short periods of time of up to about 10 minutes at levels of over 1 ppm does not typically produce symptoms. Low levels of ozone of less than 0.1 ppm normally can be tolerated indefinitely. Limits have been established by OSHA for exposure to ozone in air for breathing purposes of no more than 0.1 ppm over an 8 hour period.
Various apparatus and methods have been proposed for using ozone to purify the air in living spaces and the like and to avoid exposure of humans and mammals to levels of ozone concentration that can cause problems. Many of the proposed devices have drawbacks in operation or construction that detract from their utility.
For example, McMurray U.S. Pat. No. 4,863,701 discloses an apparatus for generating ozone for deodorizing an enclosed space. A fan supplies a stream of air past ozone generating tubes to emit a stream of ozone enriched air from the apparatus. Excessive ozone production is counteracted by an odor emitting chamber. The chamber is located downstream of the fan and after the ozone producing cycle is complete and the undesired odor eliminated, the chamber can emit a conventional air freshening odor, a perfume, that reacts with excess ozone. The chamber can be operated on a timed cycle to release the perfume after ozone production ceases so that the deodorized space does not retain a high ozone concentration after ozone production ceases. The perfume releasing device is said to guarantee that the environment that is to be occupied immediately after ozone treatment is free of potential harmful concentration of residual ozone that normally can result from ozone treatments. Thus, it is clear that the device disclosed in McMurray is not intended for use in a space occupied by humans or other mammals during ozone treatment.
Uys U.S. Pat. No. RE. 34,571 discloses an apparatus for generating ozone for use as a deodorizer and air purifier within a predetermined area. The device includes a blower unit for supplying air to an ozone generating unit. The ozone generating unit discharges ozone into the air that is supplied. A separate mixing chamber that contains air is connected to receive the air supplied from the ozone generator and containing ozone. The ozone containing air and the relatively high volume of air in the mixing chamber are mixed, the ozone concentration in the air is thereby reduced, and the ozone and excess air mixture are discharged to the surrounding atmosphere by a second blower.
Miyakami et al. U.S. Pat. No. 4,904,289 discloses a deodorizing apparatus for use in a closed chamber such as a refrigerator or the cabin of an automobile. The device is discussed in connection with a refrigerator and Miyakami shows a case having an air inlet and an air outlet and an air flow channel disposed between the air inlet and the air outlet. The inlet and the outlet to the case are separately provided with a deodorizing catalyst for accelerating decomposition of odors and ozone and minimizing leakage of any residual ozone from the case into the refrigerator compartment.
The efficiency of the deodorizing catalyst gradually decreases, which permits residual ozone to flow out from the case into the refrigerator and results in an increased ozone concentration. The ozone generator is said to be driven intermittently to maintain the interior ozone concentration below a regulation value so that the interior ozone concentration does not exceed a regulation value of 0.1 ppm before 20 years.
Perfume releasing devices, catalysts, air mixing chambers, and the associated mechanical and electronic equipment for such features for controlling exposure to ozone can be costly. These features introduce complexity to the devices and result in additional possibilities for equipment failure. Devices that are intended for use only in the absence of people and other mammals and animals are restricted in their use and may not be effective or suitable for treating air in areas that frequently are occupied for extended periods and may be subject to a variety of odors.